place the customizations in a file called "<groupname>.php" (where <groupname> is the actual name of the page group in question) in the local/ subdirectory

place the css customizations in a file called "<groupname>.css" (where <groupname> is the actual name of the page group in question) in the pub/css/ subdirectory.

These files will be automatically processed after processing any local customizations in the config.php and local.css files.

For example, to change the image displayed in the upper-left corner of pages in the "GroupName" WikiGroup, one could create local/GroupName.php containing

<?php
$PageLogoUrl = "/myimages/chess.gif";

The example's effect would cause all pages in the GroupName Wiki Group to use "/myimages/chess.gif" as the logo image instead of the default.

To add markup to the beginning or end of each page in a wiki group, see Group headers.

Per-page customizations

PmWiki also allows per-page customizations; simply use the full name of the page to be customized instead of the group. For example, one can use the file local/Chess.HomePage.php to set local customizations for Chess.HomePage.

Almost any customization that would be placed in config.php can be used as a per-group or per-page customization.

An important exception to this is setting per-group or per-page customizations for recipe scripts included in config.php. Most recipe scripts would need any customization variables defined before the script is included. Instead of using a per-group or per-page customization php file, use a per-group or per-page conditional statement in config.php, before including the recipe script. Example:

Processing order

For all local customizations, PmWiki first processes the local/config.php file, and then looks for a per-page customization file in the local/ subdirectory to process, followed by any per-group customization file. If no per-page or per-group customizations are loaded, then PmWiki loads local/default.php. If a per-page customization wants to have the per-group customizations loaded first, it can do so directly by using PHP's include_once() function.
For more information see wiki cascades.

Custom CSS styles per group or per-page

To apply CSS styles to pages of a specific group named Group Name?, create a file named GroupName.css in the pub/css/ directory and add the CSS style rules there. To apply styles to a specific page, create a file GroupName.PageName.css in this directory with your style rules. Any CSS rules to be applied for all wiki pages can be put into pub/css/local.css.

/pub/css/GroupName.css:
body { background: #F4C4B4; }

Preventing group-Level configurations

Any customization file can set $EnablePGCust=0; to prevent later page/group/default customizations from being automatically loaded. If a per-page customization needs to have the per-group customizations loaded first, it can do so directly by using PHP's include_once() function.

Authentication

Consider Wiki Farms

Wiki Groups are an easy way to host multiple sites in a single PmWiki installation by giving each site its own group. Another approach is to use Wiki Farms, which allows each site to have its own set of Wiki Group and local customization files.

Simply create a pub/css/Group.css or pub/css/Group.Page.css file containing the custom CSS styles for that group or page. See also Cookbook:LocalCSS.

Why shouldn't passwords be set in group (or page) customization files? Why shouldn't group or page passwords be set in config.php?

The reason for this advice is that per-group customization files are only loaded for the current page. So, if $DefaultPasswords['read'] is set in local/GroupA.php, then someone could use a page in another group to view the contents of pages in GroupA. For example, Main.WikiSandbox could contain:

Isn't that processing order strange? Why not load per page configuration last (that is after global configuration an per group configuration)?

Many times what we want to do is to enable a certain capability for a group of pages, but disable it on a specific page, as if it was never enabled. If the per-group config file is processed first, then it becomes very difficult/tedious for the per-page one to "undo" the effects of the per-group page. So, we load the per-page file before the per-group.

If a per-page customization wants the per-group customizations to be performed first, it can use the techniques given above (using include_once() or setting $EnablePGCust = 0;).